Skip to main content

Oregon State Flag An official website of the State of Oregon »

Accountability and BWC

Accountability and BWC

University of Cambridge

Synopsis: The use of body-worn cameras reduced citizen complaints against police in a multisite randomized controlled trial.


Community Need(s)

Complaints can negatively affect police-public relations for both officers and the community. High complaint numbers can erode public trust while at the same time wear away officers’ willingness to engage with the public. Body-worn cameras (BWC) have been recently adopted across the nation as a means to improve police-public interactions and reduce complaints.


This study expanded on similar efforts made by a study in Rialto, California. For the current study, researchers partnered with seven different agencies in two countries and used a randomized controlled trial to evaluate the effects of BWC on complaints made against officers.


Primary Research Question(s)

  1. Do BWC reduce complaints filed against officers?
  2. Whose behavior is most affect by the use of BWC - officers, suspects, or both?

Research Design

Researchers invited ten police departments to participate in the 12-month study and of these, seven agreed to the experimental protocol. These seven departments covered four jurisdictions in two English-speaking countries and included 1,429,868 officer hours across 4,264 shifts. Researchers collected the number of complaints at each site for the 12-months prior to the study and the number of complaints for both the treatment and control groups over the course of the study.

Shifts were randomly assigned to be treatment or control groups on a weekly basis, with equal numbers of day and night shifts. When officers were on shifts assigned to having cameras on, they were directed to have cameras on during all public interactions for the entirety of the interaction. 

Officers were also instructed not only to have the cameras on, but to also provide a verbal notification to subjects that the interaction was being recorded. Exceptions were to these rules were prearranged with senior agency staff and included interactions such as talking to informant and serious sexual assaults.

Each trial was monitored by a “pracademic” at each agency – graduate students who were also police officers or civilian staff. Additionally, trial integrity was monitored by comparing BWC metadata (date and time) with the date and times of experimental assignments.


  1. Researchers were not given information on the type of complaint (e.g. use of force, incivility, lack of fairness, etc.). It would be worth studying whether or not BWC affect specific types of complaints.
  2. Individual officers were part of both treatment and control groups over the course of the study.
  3. However unlikely, policies on the complaint process could have changed over the course of the experiment.


Research Findings

Across all seven sites, complaints were reduced from 1,539 complaints in the 12-months preceding the study to 113 complaints over the course of the study. This represents a 93% decrease in complaints between time periods. There were no significant differences between treatment and control groups.

Main Implications

The goal of altering behavior in a way that reduced citizen complaints was reached. To examine these results, the authors divided their discussion of results into three main sections:

A Technical Solution for Police Accountability, Legitimacy, & Police-Community Relations?

The authors discuss, at length, the tenuous relationship between complaints and police legitimacy, citing the fact that legitimacy is based on a number of factors outside of a single event that may lead to a complaint. This includes the fact that police legitimacy also relies on the views of individuals not directly involved in police interactions, recorded or not. The authors contend that further research is needed on this link, given the fact that it is so deeply entwined with the argument for implementing the use of BWC.

Contagious Accountability

Separate from the issue of legitimacy, the authors argue that BWCs do have a positive effect on police accountability, and this is a leading factor in the observed reduction in citizen complaints. The authors believe that accountability is increased due to a heightened self-awareness of officer’s actions stemming from the use of BWC. The authors take this argument further when explaining the lack of significant differences between treatment and control groups with a term coined “contagious accountability.” The authors assert that because all officers took part in both the treatment and control, they became “acutely aware of being observed more closely” even when not wearing the BWC, which meant the effect of BWC spread to all of the officer’s interactions, as well as co-workers’ interactions. It is also hypothesized that when officers wore the BWC they learned, by repeated exposure and practice, how to better manage situations, which carried over into the encounters during which they wore no BWC.

Untangling Observer Effects

The authors explore three possibilities about whose behavior is affected most by BWC in an interaction – the officer, the subject, or both. The conclusion reached is that the most affected party is the officer in the interaction since the effects of BWC carried over to no-treatment shifts. The authors assert that the “causal chain” would be: BWC + verbal warning —> officer’s reaction to suspect’s demeanor is “cooler” —> fewer complaints than without BWCs

Additional Implications

The fact that the effects of the BWC appeared in both treatment and control groups may lend itself to the argument that an entire department does not need to be outfitted with BWC, reducing costs in a time of economic constraints. Research needs to continue in the effects of BWC and police legitimacy.


Ariel, B., Sutherland, A., Henstock, D., Young, J., Drover, P., Sykes, J., … & Henderson, R. (2016). “Contagious Accountability” A Global Multisite Randomized Controlled Trial on the Effect of Police Body-Worn Cameras on Citizens’ Complaints Against the Police. Criminal Justice and Behavior, 0093854816668218.

Additional Resources

Police Foundation’s “Quantifying and Justifying the Cost of Body-worn Cameras